The present invention relates to three-dimensional (3D) time-of-flight (TOF) magnetic resonance (MR) angiography, and more particularly, to vessel enhancement and artifact reduction in 3D TOF MR angiography of the brain.
Three dimensional (3D) time-of-flight (TOF) magnetic resonance (MR) angiography is a well-known technique for imaging vessels that has been adopted for routine assessment of stenosis and occlusions of intracranial blood vessels. 3D TOF MR angiography images blood vessels based on the phenomenon of flow-related enhancement of spins entering into an imaging slice. As a result of being unsaturated, these spins give more signal than surrounding stationary spins, thus enhancing blood vessels based on the blood flow in the vessels. With 3D TOF, a volume of images is obtained by simultaneously phase-encoding in the slice-select direction. An angiography appearance for visualizing vessels can be generated using maximum-intensity projection (MIP), as is typically done with 2D TOF. Multiple 3D TOF volumes can be combined in order to visualize longer segments of vessels.
Although 3D TOF MR angiography can allow a greater resolution in the slice-select direction than 2D TOF, loss of signal may be seen with the 3D TOF method in thick volumes with slow flowing blood. Accordingly, a method for providing increased vessel enhancement in 3D TOF MR images is desirable.